This invention relates to a device for carburetting air and a hydrocarbon fuel for an internal combustion automobile engine.
It is known that a carbureter is generally comprised of a float chamber having a main fuel outlet with a nozzle directed into an induction pipe adapted to communicate with a fuel intake means of an engine. In the induction pipe a suction is developed and the fuel is drawn from the nozzle in a stream of air flowing through the induction pipe. To control the power outlet and fuel feed of the internal combustion engine, the carbureter is usually further provided with a pilot system for idling, an acceleration system, a choke valve, etc. The pilot system can slow down the engine speed by lowering the rate of the fuel-air mixture feed. If the engine speed is desired to be accelerated, the acceleration system will increase the rate of the air-fuel feed as well as the composition of the fuel in the mixture. As an automobile engine performs through a wide range of loads and speeds, the functions of the carbureter are usually complex. It must control the rate of the fuel air feed and graduate the fuel-air ratio according to the engine requirements in starting, idling, and load and altitude changes. Accordingly, the construction of such a carbureter is rather complicated.
In common practice, when the engine is started, the carbureter must temporarily supply a very rich mixture, i.e. high fuel-to-air ratio fuel feed. For this purpose, it is required to reduce the rate of the air inlet flow by closing the main air inlet with a choke valve provided upstream of the induction pipe so that air is only admitted through a pilot air passage. After the engine is fired, the rich fuel mixture is not suitable as the engine warms up. To adjust the fuel-air ratio, it has been required to open manually the choke valve to increase the rate of the air flow. However, there has been also developed an automatic system that controls the choke valve thermally. The system includes a bimetallic substance to detect the temperature and according to that temperature the choke valve is controlled.